1. Field of the Invention
The present invention relates to a sensor for detecting the wavelength and intensity of incident light. The present invention also relates to a solid-state imaging device. The present invention further relates to an imaging apparatus using such a solid-state imaging device and a method of manufacturing the same.
2. Description of the Related Art
An attempt for obtaining information about three primary colors (RGB) by a single photodiode has been conducted (see, for example, U.S. Pat. No. 5,965,875).
The photodiode as described in U.S. Pat. No. 5,965,875 has an arrangement of pixels where each pixel includes a stacked structure of three diffusion layers with different depths, 0.2 μm, 0.6 μm, and 2 μm, formed on a silicon substrate. Thus, each pixel has a three-layered structure where the layers have different depths. These layers are designed to transmit and receive light with different wavelengths, three primary colors of light (RGB: red (R), green (G), and blue (B)), respectively, based on transmitting characteristics of silicon.
For example, all the wavelengths of RGB are incident on the pixel from the surface of the silicon substrate and all of them are taken in the top layer, RG except B absorbed by the top layer is taken in the middle layer, and R except BG absorbed by the top and middle layers is taken in the bottom layer. Then, the value of R taken in the bottom layer is subtracted from RG taken in the middle layer to obtain the value of G. Subsequently, the values of R and G are subtracted from the value of RGB to obtain the value of B.
The photodiode is configured as described above, so that an image obtained by directly taking the primary colors of light can be generated in spite of including a single chip.
The above photodiode is designed to take each element out of RGB in the depth direction. However, the photodiode may not change the position for capturing electrons and further the circuit configuration thereof may be complicated, causing insufficient design flexibility. Furthermore, every pixel continuously generates independent data of information about respective colors. Thus, it is difficult to distinguish correct data from noise in a portion where the data is continuously generated and obtain RGB characteristics. Therefore, complicated software may be required for determining the RGB characteristics.
In consideration of the above, there has been proposed a sensor with a single photodiode corresponding to incident light having a structure for controlling the potential depth of the photodiode by changing a gate voltage (see, for example, Japanese Unexamined Patent Application Publication No. 2005-10114). The sensor changes the gate voltage to allow the depth for capturing electrons generated by light incident on the photodiode to be changed in response to the gate voltage, determining the wavelength and intensity of the incident light.